PTT polyester is a novel aromatic polyester product of organic polymer which together with PET and PBT belongs to the same polymer series. It is prepared through esterification and polycondensation using refined terephthalic acid and 1,3-propylene glycol as the beginning raw material.
Successful development of PTT has further enriched chemical fiber products series. Firstly, distinct from PET polyester which is almost linear in macromolecular conformation, molecular conformation of PTT polymer is spiral, which will allow PTT fiber to be highly “puffed” and endow its fiber with good elasticity; secondly, PTT polyester has a lower glass-transition temperature and thus apt to take low temperature phase transition, which can effectively eliminate influence on fabric by external stress, and allow its fiber and textile be dyed at a lower temperature with good dyeing properties of disperse dyes; thirdly the Young's modulus of PTT fiber is lower. Its textile shows very soft hand feel and good bulkiness. Its fabrics possess good elastic recovery function, and thus called “Memory Fiber”.
Because of above advantages, PTT polyester and its fiber are widely and fast popularized in chemical fiber field. Up to now, the following two aspects are most widely used in the market: In one aspect, parallel composite elastic fiber that has elastic function similar to polyurethane fiber and obtains very good effects with its textile having very good elastic recovery and bulky function when used in fabric substituting for polyurethane fibre is spinned making use of the different shrink function of the two composition PTT and PET; In another aspect, conjugate spinning or combing with other fibers is conducted making use of the lower glass temperature and the easiness to take phase transition upon friction at normal temperature owned by its fiber, so that the flatness variation of the fabric caused by outer force will be eliminated, making the fabric easier to take care, producing effect of “one touch smooth”, and fabricating so called “Memory Fabric”.
Over the years, people have done a lot beneficial modification to conventional polyester PET, so that modified terylene gains a lot excellent performance and thus be widely used. Great progress has been seen in the diversity and comfort aspect. Seen from applicability aspect, PET polyester fiber among all types of human synthetic fibers is most suitable for human need and also a most widely used polyester fiber at present. Although PTT fiber possesses its unique advantages, there are still certain defects in some performance aspects. Therefore, besides to enlarge the application of conventional PTT fiber, modification and differentiation of PTT polyester and its fiber must be done cooperating with development of modified PET polyester fiber in order to better use features of PTT fiber.
PTT polyester has unique molecular structure with molecules being apt to approach to each other. Therefore, PTT polyester possesses crystallization property similar to Nylon 6. Its crystallization speed during spinning is fast and crystallization degree is high. Minor variation of spinning condition can change inner structure of PTT fiber, leading to different uniformity of the fiber, which will bring great difficulty to adjustment of spinning process. In addition, in prior art, spinning of PTT polyester is generally carried out at a relatively low temperature in order to prevent degradation of melt, as a result, color bar or chromatic difference is formed due to insufficient crystallization of fiber during winding and stretching process. Although the fabric thus obtained has good hand feel and quality, phenomena that the fiber recrystallizes under tension when stretched by outer force exist during starching, weaving, printing and dyeing process and even for ready-made clothes. The fabric is apt to form chromatic difference and color bar during weaving, printing and dyeing process, and for ready-made clothes lead to scratch and white bar forming mechanical damage that is unrecoverable. All the time, these defects have been restricting the application of fiber of PTT polyester and leading directly to difficulties in caring of PTT fabrics and clothes.